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MOT fail help


omalleym

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Car has failed for 2 reasons:

1. Reg plate light doesn't come on when lights are on.  However, I have since discovered that they do come on when the rear fog light switch is on.

2. Rear fog light not working

Would really appreciate any help and how easy it is to redo wiring and replace bulbs if needed.

Thanks 

M

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Sounds more like the tester getting the switch gear mixed up.  Rear fogs will only work if lights are on.  Check yourself before taking what the tester has said a word!

Beyond that check fuses, bulbs and make sure the bulb holders are clean and not corroded.  Unless the wiring has been fiddled with I doubt the issue is there at this stage.

 

 

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thanks Nige as I never use the fog lights Im not quite sure where they are located.  My model year is 1987 so I presume they are in the central reflector section?

I did check the lights myself afterwards with the headlights on.  Reg plates lights work but only when the rear fog switch is pulled out.  Couldn't get the fog lights on at all.  All I could see was the rear brake lights.

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OK, that does sound like the wiring harness behind the rear bumper has got mixed up for the fogs and number plate lights.  Access to what has been done might be a faff as it might involved removing the rear bumper.

87 will have them integrated into the reflector.

I reckon you'll have redundant harness for the reg plate dangling somewhere around the exhaust and the fog light harness connected to the reg plate lights.

Have you had any work done recently that had required the rear bumper to be remove or exhaust.  Assume this is a recent problem as it passed the MOT last year?

 

 

 

 

They are the correct lights for the reg plate.

That bumper looks nice, shiny and freshly paint.

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That is strange then, maybe the previous tester didn't notice it or it's something new that has failed, I suspect the former.  I think you're going to have to get you eyes up around the back and see if you can see anything amiss.

Removing the reflector bar to check if it's connected up could help, though that does have it's perils of broken clips and cracked reflector.

Somebody might have a better suggestion but it will probably involve multimeters and other dark arts equipment.

 

I'm sure the connectors are quite different though, the reg plate is small spade connectors as it has to be passed through the rubber bumperette.  The fog light has a proper plastic plug on the end so quite difficult to mix up.  Though all that can be cut and fiddled with.

 

Edited by Nige
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If they removed the bumper or exhaust/engine then maybe so, otherwise unlikely.

Crappy photo from my build thread but what I have highlighted in red is the harness for both the reg plate light and fog.  Just where is drapes over the exhaust pipe is where it splits into two tails one for the fog and the other for reg plate, there is also the same on the other side of the car.  They are normally clipped onto the inside edge of the bumper.

I reckon this has been mixed up, with one being left redundant. 

 

wire.jpg

Edited by Nige
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I'd have a rummage/eyeball around first and if you find a pair of connectors not hooked up to anything then that could be your problem.  Then you might have to start thinking about removing the bumper or even just the rear exhaust muffler.  All depends how small your hands are I guess.  It's a while since I've looked up there and mine isn't standard these days anyway.

 

Some further pictures here that might help you identify stuff

https://blog.fcpeuro.com/how-to-add-license-plate-lights-to-an-air-cooled-porsche-911

 

 

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25 minutes ago, SilverWT said:

Remember, fog light switch pulled out = front fogs on, knob on switch turned clockwise = rear fog lights on (with the headlights on).

 

Mark

On the dash I have what looks like two fog light switches.  Red which I presume is for the rear and green which works the front fogs.  Is that not the case and you have to also turn the front fog switch to the right?

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Spoke to the mechanic who worked on it in April and he didn't touch it so I think it has been like this for a while just not picked up on the MOT.  I went under the car this evening and as Nige said you need small hands to get at the connectors.  I've decided to have a mechanic look at it this Saturday as I'm sure bits will have to come off.  Will keep you all posted and thanks so much for all your help.

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2 hours ago, omalleym said:

Spoke to the mechanic who worked on it in April and he didn't touch it so I think it has been like this for a while just not picked up on the MOT.  I went under the car this evening and as Nige said you need small hands to get at the connectors.  I've decided to have a mechanic look at it this Saturday as I'm sure bits will have to come off.  Will keep you all posted and thanks so much for all your help.

Bit of experience here because I've just rewired and fitted my rear light looms last week (87 model too) . I doubt the wire have got swapped. The number plate lights have small spade type terminals, where as the fog lights have a twin round pin connector. 
Also from factory each set of lights are fed from loom on that side. e.g. left reg-plate light and left fog light fed from left side loom. So unless it's been spliced and bodged, It could be the switch side or fuse box.

Firstly check the rear looms. If you pull the plug form inside the engine bay (just above the engine mounts at the back either side) there'll be a seven pin socket. Connect the center pin to negative, Pin 1 to positive for reg plate light, pin 6 to positive for Fog lights. I think they count from the notch but the pattern is (clockwise)

1  reg plate

2 Indicator

3 Stop light

4 rear lights

5 Reverse

6 Fog light

I'm in the middle of doing my wiring so if you want anything checked or pics let me know. wiring diagram of the lights attached, might be helpful.


 





 

wiring_lamps.jpg

Edited by TargaWayne
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2 minutes ago, TargaWayne said:

Bit of experience here because I've just rewired and fitted my rear light looms last week (87 model too) . I doubt the wire have got swapped. The number plate lights have small spade type terminals, where as the fog lights have a twin round pin connector. 
Also from factory each set of lights are fed from loom on that side. e.g. left reg-plate light and left fog light fed from left side loom. So unless it's been spliced and bodged, It could be the switch side or fuse box.

Firstly check the rear loom. If you pull the plug form inside the engine bay (just above the engine mounts at the back either side) there'll be a seven pin socket. Connect the center pin to negative, Pin 1 to positive for reg plate light, pin 6 to positive for Fog lights. I think they count from the notch but the pattern is (clockwise)

1  reg plate

2 Indicator

3 Stop light

4 rear lights

5 Reverse

6 Fog light

I'm in the middle of doing my wiring so if you want anything checked or pics let me know. wiring diagram of the lights attached, might be helpful.


 





 

wiring_lamps.jpg

thank you so much, I will give that a go.

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9 hours ago, Nige said:

Removing the reflector bar to check if it's connected up could help, though that does have it's perils of broken clips and cracked reflector.

 

The later reflector bar has fasteners under the top rubber and are much easier to remove.

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